Air conditioning system



April 1942- J. P. MILAR AIR CONDITIONING SYSTEM Filed Nov. 18, 1938 NN RN mm RN RN Patented Apr. 28, 1942 John P. Milar, Chicago, 111., assignor to Pullman- Standard Car Manufacturing Company, Chicage, 11]., a corporation of Delaware Application November 18, 1938, Serial No. 241,213

13 Claims.

The present invention relates to a control system, and as one of-its principal objects it is intended to provide an efllcient and simple means for removing from a motor its load prior to starting' and stopping of the motor. a 7

As another object it is intended to provide a means for gradually loading the motor while running at a reduced speed and then increasing the motor speed to full speed operation.

Other objects and advantages will become ap-..

parent as the disclosure proceeds and the description is read in conjunction with the accompanying drawing, in which Fig. ,1 is a schematic drawing of a complete air conditioning system; and

Fig; 2 is a wiring diagram of the electrical circuit used in operating the air conditioning system shown in Fig. 1, the heavy lines indicating the main electrical circuit from the D. C. source of current to the D. C. motor, while the lighter lines indicate the control circuit.

Aspeciflc embodiment of the present invention is selected for. the purpose of disclosure only, and is not intended to place unnecessary limitations upon the claims. It is intended that the claims shall be construed as broadly as the prior art will permit. I

The invention is shown as it applies to an air conditioning system, but it is recognized that it has many other applications. Wherever there is a motor driving a load, 'and it is desirable to unload the motor prior to its starting and stopping, the invention is applicable. In the present disclosure the motor drives a compressor for producing refrigeration to cool the interior of a railway er car. Under normal operating conditions the demand for cooling is not constant, so that the compressor operation is intermittent, resulting in repeated startings and stopplnss of the compressor, and consequently the compressor drive,

When the motor is running under load, approximately 250 amperes of current are passing through the main circuit. If the motor is stopped under these conditions there is substantial arcing across the contact points which causes burning ofthe points of the switch and even results in the switch points becoming welded together.

when the load is removed from the motor drive and the motor is allowed to idle, a current of only about 30 amperes is required, so that there is practically no arcing when the circuit is opened under these conditions. For this reason it is desirable to unload the motor not only when starting but also tem.

Referring now to Fig. 1,- a refrigeration system is shown including a compressor III, a conwhen stopping the sysdenser i l a receiver I 2, an expansion valve I3,

and an evaporator l4, positioned in a duct 15 at the exhaust and of a blower fan It. The var-.

ious elements of this refrigeration system are interconnected by piping ll, which conducts the refrigerant through the usual refrigeration cycle. The duct I I discharges into the car body through vents l8, spaced at intervals along the lengthof the car.

The compressor is is driven either by a D. C. motor i9, or by an A. C. motor 20, through a shaft 2! and a clutch 22. The D. C. motor is receives its electrical energy either from a battery 25 or from an axle generator 26, shown in Fig. 2. This generator is driven from the car axle 21 through a belt-or other suitable means 28. The A. C. motor 2|! receives its current from an outside source which is plugged in at 29.

D. C. operation When the air conditioning system is placed in operation the first act is to close a blower fan switch", which is situated on the master control panel, generally located'at one end of the car. The closing of this switch immediately completes a circuit from a positive terminal ll 'of a D. C. source of current through a conductor 3!, switch 30, conductors 33 and 34, to the blower fan It, and thence to the negative side of the source of current through conductors 35 and 36, fan switch 30, and conductor 31. Under these conditions the blower fan I is operating to blow air into the car body through the duct l5 and.

vents It.

The positive and negative terminals 3i and 24,.respectively, are indicated as being entirely separate from the battery 25 or the axle generator 28, but it is to be understood that they actually are in the battery and generator circuit. The entire showing in Fig. 2 is schematic, and theparticular placing of these two terminals is done for the sake of convenience and to sim plify the disclosure.

.The next operation is t close a circuit at the selector switch 38, which also is generally situated on the master control panel, and, depending upon the position of the selector switch 38, one of the thermostats 39 or 40 is placed in the control circuit. Each of these thermostats 39 and 40 has a definite temperature at which it functions to closethe control circuit, and for thepurpose of illustration it is assumed that thermostat I! is set to operate at F., and the thermostat ll is set to operate at F. j

Assuming that the selector switch 38 is set for 75, when the temperature in the car reaches this value the thermostat 39 closes a circuit from the positive terminal 3| through the blower fan switch 3|, conductors 33, 4|, selector switch 88, conductor l2, thermostat is, and back through conductor 43, cooling pilot relay 44, conductors mally held in a closed position when the voltage of the battery 25 is normal, and then back through conductor 58, Y relay 5|, and conductor 52 to the negative terminal 24. Current also passes from the low voltage switch'relay 49 through a T relay switch |3|', through conductor 53, D. C. contactor relay 54, conductor 55, and back to the negative terminal 24.

The D. C. contactor relay 54 is a quick-make slow-break relay. Immediately upon closing of the cooling pilot relay 44' the D. C. contactor relay 54 is energized, snapping D. C. contactor relay switch 54 -to a closed position.

Car standing still While the car is standing stillin a station or along the right of way, the condition of the electrical circuit is as shown in Fig. '2, so that current from the battery 25 flows from the positive terminal 3| through conductors 56 and 51, and then a portion, of the current passes through the resistor 58, the remainder passing through a current coil'59; then they join and pass through the conductor 60, D. C.,contactor switch 54', which has been closed by the D. C. contactor relay 54, and then through conductors 6| and B2. to the commutator brushes 63 and motor field 64, respectively, and thence back to the negative terminal 24 of the battery 25 through the conductors 65 and 66.

In the circuit of the D. C. motor field 64 is a motor field relay switch 61', which is normally held in closed position, as shown in Fig. 2, and is opened by the energization of a motor field relay 61. As long as the D. C. motor I9 is drawing from the battery 25 this motor field relay 51 is de-energized and the switch 61 is closed, so that the motor I9 is operating with a strong field 64 at a reduced speed.

After a time delay of from two to five seconds, during which time the D. C. motor I9 has built up its speed, the Y relay 5| operates to close the Y relay switch 5|, thereby closing a, circuit from the positive terminal 3| through the conductor 58, Y relay switch 5|, resistor 69, conductor 10,

condenser fan motor 1|, and electric clutch 22,.

which are connected in parallel, and thence back through conductor 12 to the negative terminal 24. The closing of switch 5| also completes a circuit from the positive terminal 3| through conductor 68, switch 5|, resistor 69, S relay switch I3, and thence back to the negative terminal 24 through conductor 52. sistor 69 in this last circuit, however, prevents the energization of the S relay I3 to the extent where itacan close the S relay switch 13'.

Under these conditions the condenser fan motor commences its operation, and the electric clutch 22 becomes partially energized to drive the compressor l0. Because of the presence of theresistor 89 in the electric clutch circuit, the clutch is only partiallyv energized, so that there is a lag between the speeds of rotation of the compressor l and shaft 2|. As the con- The presence of the rethe D. C. motor l9.

denser fan motor 1| builds up in speed it produces a counter-electromotive force which reduces the current through the condenser fan circuit, thereby permitting an increased amount of current to pass through the S relay l3 and increasing the energization of the S relay and closing the S relay switch I3. The closing of this switch cuts out the resistor 89, and causes the condenser fan motor II to operate at full speed and the electric clutch 22 to become fully energized. The removal of the resistor 69 from the S relay 13 permits sufficient current to fiow through this circuit to energize the S relay l3 sufficiently to maintain the switch 13' in closed position. There is now a positive drive between the D. C. motor l9 and the compressor l0 through the electric clutch 22, and refrigeration is being produced to cool the car.

When the car has been cooled to 75, so that the thermostat 39 is no longer calling for cooling, the cooling pilot relay 44 is de-energized, opening the pilot relay switch 44', thereby immediately de-energizing the Y relay and opening the Y relay switch 5|. This operation opens the circuit to the condenser fan motor H, and the electric clutch 22, thus removing the load from After a time delay of from two to five seconds, the D. C. contactor' relay 54 becomes de-energized, opening the contactor switch 54' and de-energizing the D. C. motor I9. The motor is thus stopped after first completely removing the compressor load from the shaft 2|.

Car in motion-speeds up to miles an hour When the car is in motion the axle generator 26 rotates in a direction corresponding to the direction of the car movement. The usual field reversing switch, generally indicated at I25, is provided to maintain a unidirectional flow of current from the axle generator 26, regardless of the direction of travel of the car, and since its operation is well known in the art and it forms no part of the present invention a detailed deis described above.

The axle generator 26 produces current which flows from the positive terminal 3| through conductors I4, 15, generator regulator relay I5, conductors I1, 18, and then the current splits, a portion passing through the series coil 19 and a portion passing through a resistor 80, and then they join and pass onthrough conductor 8|, potential coils 82 and 83, and back to the negative side of the generator through conductors 84 and 85. i I

-The current also passes through the conductors l4, I8, 85, and through a holdingcoil 86,- conductors 81, 88, field teaser 89, carbon pile 90, conductor 9|, field reversing switch blade 92, conductor 93, generator field 94, conductor 95, a second blade 96 of the field reversing switch, and thence to the negative terminal of the generator 26. This latter circuit energizes the axle generator field 94, and since it includes the field teaser 89 the strength of the field at speeds below twenty-five miles an hour is considerably limited, so that the generator output is small.

The generator current also passes from the positive terminal 3| through conductors 14, I5, a conductor 91, a relay 98, conductors 99 and I00, a relay IOI, conductors I02, ll, 18, where it splits and passes through the series coil 19 and resistor, and then on through conductor 8|.

potential coils 82 and 83, and thence back to the negative terminal through the conductors 84 and 85.

As long as the car is traveling below twentyfive'mile'san hour the field teaser 89 limits the strength of the field 94 ,to the extent that relay IOI, though energized, is not suiiiciently strong to close the relay switch IOI. When the car speed reaches twenty-five miles an hour, however, relay IOI closes the switch IOI', cutting out the field teaser 89 by permitting the current to pass from conductor I through conductors 91, I03, relay switch IOI, carbon pile 90, conductor I04, field reversing switch blade 92, conductor 93, generator field 94, conductor 95, field reversing switch blade 96, and thence back to the negative terminal. When the field teaser is removed from the circuit the generator field becomes fully energized, thereby stepping up considerably the generator output, and I this, increased output strengthens the series coil I9.

A generator relay, generally indicated at I05, includes the series coil I9, the potential coils, 82 and 83, andthe holding coil 86, a core I26, about whichis wound the series coil I9 and potential coil 82, an armature I06 which passes through the potential coil 83, the holding coil 86, and a generator relay switch I0I fulcrumed at I08. The potential coils 82 and 83 oppose each other since they are acting on the switch I01 on opposite sides of the fulcrum I08, and they are of equal strength, so that the slightest variation in strength of the holding coil 86 will overcome the balance between the actions of the potential coils 82 and 83, thereby moving the switch I01. When this switch has once been closed the series coil I9 holds it in this position until theoutput of the axle generator 26 is limited below a predetermined amount corresponding to a vehicle speed oi about twenty-fiv miles per hour.

When switch M! has been closed by the generator relay, current flows from the positive terminal 3| of the axle generator through conducpresent invention and, since its operation is well known in the art, a detailed description is believed unnecessary. For present purposes, it is sufiicient to state that the relay functions to maintain an open circuit from the generator to the battery or to the D. C. motor circuit as long as the generator output is below the battery voltage, which is the case when the car is operating below miles' an hour. When the generator voltage exceeds the battery voltage, the generatorrelay operates to close switch I01, thereby permitting the generator to charge the battery and supply current to the D. C. motor circuit.

whose resistance is varied in response to the generator output, and since this carbon pile is in the generator field circuit the strength of the field varies conversely with the amount of resistance in the carbon pile. Thus as the car speed increases above a predetermined rate the increase in the generator output causes the carbon pile to insert more resistance into the generator field circuit, thus limiting the generator output.

The low voltage relay switch 49 is normally held in a closed position by a voltage coil II I, which is impressed with the voltage of the battery 25 or the axle generator 26, depending upon which source of current is in the circuit. Under these conditions current fiows through the voltage coil III and the resistor II2 to either the conductor H3 or the conductor H4, depending upon which source of current is in the circuit. When the voltage is low, due to battery weakness, or to other conditions, the voltage coil will not have suflicient strength to maintain a closed circuit through the undervoltage relay switch 49, so that the control circuit will function to first deenergize the electric clutch by de-energizing the Y relay 5|, and then will shut 'down the motor by de-energizing the D. C. contactor relay 64.

When theundervoltage relay switch 49 is open it may again be closed by pushing a reset button I I5, which momentarily energizes the voltage coil III and closes the switch 49, and if the line voltage is up the voltage coil III will maintain a closed circuit. If, however, the voltage is still down the undervoltage relay switch 49 will immediately reopen.

Upon starting of the D. C. motor there is a surge in the flow of current through the D. C.

motor circuit which momentarily reduces the voltage across the line, so that the voltage coil .I II would momentarily be partially deenergized. To prevent opening of the undervoltage relay switch 49 under these conditions the current coil 59 is placed in tandem with the voltage coil III, and when this surge occurs this current coil maintains a closed circuit through the undervoltage relay switch.

The output of the axle generator 26 is limited by a generator regulator, generally indicated at IIO, which includes the usual carbon pilg: 90,

When the D. C. motor is operating from the battery it is desirable to decrease the strength of the motor field 64, so as not to overload the battery, but when the axle generator 26 is supplying current to the motor a switch I I6 is closed, energizing the motor field relay 61, thereby opening the motor field relay switch 61' and placing resistance in the motor field circuit to cause the motor to operate at full speed. The switch H6 is closed only when the generator relay switch I0I'is closed.

A. 6'. Operation The transfer switch I30 is placed in the control circuit for the purpose of permitting the A. C. motor 20 to drive the D. C. motor I9 as a generator, to charge the battery 25, at a time when car cooling is not required. In the conventional equipment, the battery is charged by means of an outside D. C. source which placed across the battery terminals when the car-is in a station where such facilities are available, and no provision whatever is made for employing the A. C. motor to drive a car generator for charging purposes.

In the present arrangement, the A. C. motor is generator to charge the battery or to drivethe' D. C. motor I9 alone with the compressor remaining idle at a time when air cooling is not required.

Assume for present purposes that the car is standing in a station where an outside source of alternating current is available, and temperature conditions are such that car cooling is required. The transfer switch I30 will be in the cooling position as shown in solid lines in Fig. 2. When either of the thermostats 39 or 40 calls for cooling, the cooling pilot relay 44 is energized, as previously explained, closing pilot relay switch 44', so that the current flows from the positive terminal 3| of the battery through the blower fan switch 30, pilot relay switch 44', high-low pressure switch 46, conductors 41 and 48, tothe transfer switch I30 where the current divides, part of it fiOWil'lg through the conductor plate I34, conductors H9 and I20, short |2|, phase relay switch II8, A. C. contactor relay- I23, and then back to the negative terminal 24 of the bat-v tery through conductors I24 and 46 and blower fan 30. The A. C. contactor relay I23 is thus energized to close switches I23, I23", I23, and |23", thereby placing into operation the A. C. motor 20. The current passing through phase relay switch 8 also flows through conductor I33, T relay I3I, then through conductors I24 and 46, and blower fan switch 30 to the negative terminal of the battery 24. The T relay |3I is thereby energized to throw the switch I3 I to the dotted line position so that the current also flows from the conductor I33 across the T relay switch I3I', then through conductor 53, D. C. contactor relay 54, and back to the negative terminal 24 of the battery through conductor 55.

The D. C. contactor relay 54 is thereby energized to close the D. C. contactor switch 54' so that the D. C. motor I9 is being driven as a generator by the A. Cfmotor 20 to charge the battery 25, The second path which the current flowing through the transfer switch I30 follows is through conductor I32, low voltage relay switch 43 (normally held in a closed position), conductor 50, Y relay 5|, and then back to the negative terminal of the battery 24 through conductor 52. After a time delay or from two to five seconds, Y relay 5| operates to close the circuit to the electric clutch 22 and the load is gradually applied as previously described.

When thereis no need for car cooling, as is the case in the winter time, the transfer switch I30 is turned to the dotted line position shown in Fig 2 so that, when the car is standing in a station where a source of alternating current is available, the battery 25 may be charge'd'at a time when the compressor remains idle. Under these conditions, the current flows from the positive terminal 3| through the blower fan switch 30, conductor 4|, transfer switch I30 (in the dotted line position) ,conductor II9, short I2I,'phase relay switch I I8, and then through both the A. C. contactor relay I23 and T relay I3l, as previously described. Thus the T relay switch |3| is held in the'dotted line position, and the D. C. contactor relay 54 is energized, as previously explained. With'the transfer switchin this position, however, the circuit through conductor I32,

low voltage relay switch 49, and the Y relay 5| is open so that the electric clutch 22 remains deenergized, the compressor I0 remaining idle.

When the cooling thermostats are calling for cooling, the control circuit functions as before to close the circuit through the Y relay switch 5| and S relay switch 13', thereby allowing current to flow from positive terminal 3| of the current source through these two switches, conductor 12, D. C. motor field relay 61, and then through conductor I35, switch 23"" (which is held in the closed position by the A. C. contactor relay I23), and then back to the negative terminal 24 of the current source through conductors I24 and 46 and. blower fan 30. The D. C; motor field relay 61 is thus energized to open the field relay switch 61', thereby placing resistance in the field 64 of the D. 0. motor (now acting as a generator) to limit the generator output. In this manner, the generator output is reduced at a time when car cooling is required, and the load on the A. C. motor is at a maximum; but, when car cooling is not required, the control circuit causes the D. C. motor field relay 61 to become energized, thereby closing switch 61' to increase the strength of the motor field 64.

The condenser fan 1| is connected in parallel with the S relay 13, and it functions as a timev to running speed, the demand for current in this circuit is greatly lessened so that the current flow through 8 relay 13 builds up to the point where S relay switch 13 is closed, thereby cutting out the resistor 69 and fully energizing the electric clutch 22.

The explanation for the diminishing demand for current through the condenser fan motor 1| may be found in Elements of Electricity, by W. H. Timbie, first edition, 1912, page 203. The principle, briefly, is as follows: When the circuit to an electric motor is first closed, the demand for current is great, but as the armature commences to rotate the lines of magnetic flux are being cut by electrical conductors so that there is a counter electro-motive force generated by the motor which may be thought of as setting up a resistance to the flow of current through the motor. -It is the effect of this electro-motive force which reduces the current fiowthrough the condenser fan motor circuit.

What I claim is:

1. A motor, a source of energy for driving the motor, a load driven by the motor in response to an intermittent demand, a clutch between the motor and the load, and control means responsive to the demand for the load for controlling the operation of the motor including a quickmake, slow-break relay for connecting the motorto the energy source, and a slow-make, quickbreak relay for controlling the clutch operation.

2. An electric motor, a load driven by the motor in response to an intermittent demand, an electric clutch between the motor and the load, a source of electrical energy for driving the motor and energizing the clutch, and control means responsive to the demand for the load for controlling the operation of the motor including a quick-make, slow-break relay for connecting the motor to -the energy source, and a slow-make,

2,281,244 current when the pilot relay is closed, said conquick-break relay for controlling the energize.- tion of the clutch.

} 3. A motor, a source of energy for driving the motor, a compressor driven by the motor, a clutch between the motor and the compressor, and control means responsive to requirements 7 for compressor operation for controlling the motor operation including a quick-make, slowbreak relay for connecting the motor to the energy source, and a slow-make, quick-break relay for controlling the clutch operation.

4. A motor, a source of energy for driving the motor, a load driven by the motor in response to an intermittent demand, a clutch between the motor and the load andcontrol means responsive to the demand for the load for controlling the operation of the motor including a quickmake, slow-break relay for connecting the motor to the energy source, a slow-make, quick-break relay for controlling the clutch operation, means for driving the load from the motor at a reduced speed when it responds to the making of the last named relay, positive drive through the clutch thereby driving the load at full speed.

5. A motor, a load driven bythe motor, an electric clutch between the motor and the load, motor'control means for operating the motor including a source of energy and means for quickconnecting the motor to the source of energy when starting the motor and slowly disconnecting the motor from the source of energy when stopping the motor, a clutch control circuit including a source of electrical energy, a resistor and a slow-make, quick-break relay for closing the circuit to the clutch, ,a' relay responsive to the clutch circuit for removing the resistor from said circuit and control means responsive to the requirements for the load for actuating the motor control means and the clutch control, circuit.

of the clutch at slow speed, and time delay and a relay for establishing a 6. A motor, a load driven by the motor, a multi speed clutch between the motor and the load, motor control means for operating the motor including a source of energy and means for quickly connecting and slowly disconnecting the motor from the source of energy when .starting and stopping the motor respectively, a clutch control including means for slowly establishing a slow speed drive. through the clutch and for quickly declutching, a control means responsive to the requirements for the load for actuating the motor and clutch control means, and time delay means for changing the clutch drive to high speed drive. 7. An air conditioning system including a compressor, condenser, an evaporator, and means for driving the compressor, clutch means between the driving means and the compressor, and a control circuit including a thermostat, means responsive to the'ther'niostat tor energizing the compressor driving -means, generating means, time delay means for energizing the generating means, and means responsive to the output or the generating means for energizing the clutch means so as to positively drive the compressor.

\ 8. An air conditioning system including a compressor, and a motor driven condenser fan, a

motor for driving the compressor, an electric clutch between the motor and the compressor,

I and a source of power for driving the motor and energizing the electric clutch, and a control circuit including a thermostat, a cooling pilot relay 1 energized by the completion oi the circuit through the thermostat, a quick-make, slowbreak contactor el y energized by the source oi tactor relay closing the circuit to the compressor motor, a slow-make, quick-break relay energized by the .source of electric current when the cooling pilot relay is closed for completing the circuit to the condenser fan motor and the electric a predetermined interval of time.

9. A motor; a source of energy for driving the motor, a load driven by the motor in response to an intermittent demand, a multispeed clutch between the motor and the load, and control means responsive to the demand for the load for controlling the operation of the motor including a quick-make, slow-break relay for connecting the motor to the energy source, a slow-make, quick-break relay for controlling the operation means acting in time delay relationship with respect to the slow speed operation of the clutch for placing the clutch in high speed operation.

10. A motor, a source of energy for driving the motor, a load driven by the motor in re sponse to an intermittent demand, a'multispeed clutch between the motor and the load, and a control circuit responsive to the demand for the load for controlling the operation of the 11. The combination of a load, a motor for driving the load, ing power 'tothe a source of energy for iumishmotor, means for starting the motor and operating the motor at slow speed with the load disengaged from the motor drive, time delay means for gradually placing the load on the motor drive, and time delay means for increasing the speed oi operation of the motor. K

- 12. The combination 01' a load, a motor for driving the load, a source of energy for the motor.

.low speed, means acting in time delay relationor the motor reship with respect to the starting sponsive to the first named means operating on the driving ratio to'its full driving between the motor and the load ratio for normal operation, and

means acting in time delay relationship with reto the secondtime delay means for increasir g the motor speed to normal operating speed.

JOHN r. Miran means for increasing motor speed 

